1. Field of the Invention
The present invention relates to remote transmitter systems and methods for vehicle applications and to interference reduction in communications systems.
2. Background Art
Remote transmitter systems are used in a number of vehicle applications. For example, remote keyless entry (RKE) systems allow a remote transmitter to be carried by a user and a receiver mounted in the vehicle to receive the transmitted signal and in response, lock or unlock the vehicle, etc. A remote keyless entry (RKE) system for the automotive market or any other communications system that uses radio frequencies to transmit information from one location to another without using wires is susceptible to interference from other radio frequency communications systems. If the interference is high enough, communication between the transmitter and receiver can be degraded severely.
Some existing radio frequency communications systems and methods are described in U.S. Pat. Nos. 4,387,469; 5,197,084; 5,499,388; 5,532,683; 5,555,451; 5,867,776; 5,940,746; 6,021,314; 6,049,294; 6,246,867; and 6,256,477. Although some existing remote transmitter systems and methods have been commercially successful, there is a need for an improved remote transmitter system and method for vehicle applications.